1. Field of the Invention
The invention relates to a two speed planetary gear drive axle assembly wherein a slidable sun gear is moved between two axially spaced operative positions and, more specifically, to means for preventing the sun gear from contacting the differential mechanism.
2. Description of the Prior Art
U.S. Pat. No. 3,413,873 which issued to L. A. Bixby on Dec. 3, 1968 discloses a two speed planetary drive axle of the type to which the present invention is particularly applicable. The Bixby patent discloses a sleeve type sun gear which is axially movable between a high speed position where the sun gear sleeve is locked in position to rotate with the planetary gear support and a low speed position where the sleeve is locked against rotation relative to the axle housing. The sun gear sleeve is concentric with one of the drive axle shafts and axially movable between the aforesaid positions by means of a yoke pivotally mounted to the differential carrier. The yoke may be moved by an air motor or a solenoid and, prior to the present invention, the sun gear sleeve has been moved in one direction until it contacts a side gear of the differential mechanism. This applies an undesirable thrust to the differential mechanism and, when the side gear and sun gear sleeve are rotating at different speeds, the friction between the two gears increases the temperature within the differential case and causes unnecessary wear of the associated parts.